Street lamp, the essential road illumination equipment in people's daily life, has been widely used in streets and squares to lighten nearby area in dark night. Based on its wide and frequent use, the street lamp is required to afford sufficient illumination intensity and long service life. Most traditional street lamps are incandescent lamps and high voltage sodium lamps. However, LED, with advantages of high efficiency, energy saving, environmentally friendly and long service life, has become common use, and the trend of replacing the traditional street lamps with LED street lamps is ongoing. Yet, the amount of traditional street lamps is so large that to complete the replacement in a short time frame is hard to achieve. Besides, LED still has some problems with suitability and heat dissipation, so if most existing traditional street lamps are to be replaced by LED street lamps, there will be a great many structure components needing to be changed, thus increasing the replacement difficulty and wasting replaced street lamp housings and wires. Since LED produces relatively high heat energy, it is critical to ensure LED radiate heat energy effectively after the replacement. Moreover, if the replacement is to be carried out, LED street lamps are required to have intact integral structure, thus causing relatively high cost. It is thus clear that the problems aforementioned will hinder the popularization of LED street lamps, and necessary and targeted technical improvement shall be made during the popularization.